I would say your last point balances out the others to show why productivity did not increase as much as you would expect!

Nah, spreadsheets did that on their own. Have you ever actually found a usable spreadsheet?

Different levels of usability.

Spreadsheets as simple ledgers? Wonderful, assuming you know about using ranges and how to use $ (or not) as part of reference statements.

Even that level of complexity seems like wizardry to most office drones.

However a spreadsheet is weak compared to a true relational logic engine; a modern database. Databases /have/ had the decades of refinement and are very good tools. Yet for those tools you kind of nail it. Specialists are required to correctly harness that potential.